Manufacture of hollow metallic balls from sheet metal.



N 812,135. PATENTED FEB. 6, 1906.

A. JOHNSTON.

MANUFACTURE OF HOLLOW METALLIC BALLS PROM SHEET METAL.

APPLIOATIQN FILED MAR.3.1905.

vwemtoz witness W UNITE STATES PATENT OFFICE.

MANUFACTURE OF HOLLOW METALLIC BALLS FROM SHEET METAL.

Specification of Letters Patent.

Patented Feb. 6, 1906.

7 Original application filed Aprill, 1902, Serial No. 101,419. Divided and application filed August21,1903, Serial No. 170,371. Again divided and this application filed March 8, 1905. Serial No. 248,310.

To all whmn it may concern:

Be it known that I, ALLEN JOHNSTON, of Ottumwa, Iowa, have invented a new and useful Improvement in the Manufacture of Hollow Metallic Balls from Sheet Metal, which invention is fully set forth in the following specification.

On April 4, 1902, I filed application Serial N 0. 101,419 for improvements in ball-bearings and balls therefor. A division of said application was filed August 21, 1903, Serial No. 170,371. This application is a division of both said applications.

In the manufacture of hollow metallic balls from sheet metal by first forming a blank a into a cup and then closing the open end of ball is often bulged slightly before the dies come together, or the dies scrape or shear off a portion of metal from the surface with which they contact, with the result that ribs or burs are frequently formed on the ball, destroying its smooth spherical form, and if such balls are used at all necessitating further expense-adding operations to remove saidribs or burs. These difficulties and objections are overcome by the improved process constituting my present invention, in accordance with which the sheet-metal blank is formed into a cup having a diameter less than that of the ball which it is to form, and the cup then closed and swelled or expanded to form a ball of larger diameter than the cup. The closing and swelling or expanding of the cup are preferably though not necessarily performed simultaneously by the closingdies. Practical experience has demonstrated that by thus providing for expansion or swelling of the cup, the latter is enabled to more accurately adapt and shape itself to the dieopenings and form a ball which more nearly approaches a perfect sphere.

I preferably form the cup from a square sheet-metal blank, as such blanks may be cut from a long strip of metal without waste. Furthermore, the four points or apices of the i into cups.

edge enables cups formed from such blanks to be closed .to greater advantage than cups made from other forms of blanks; but in forming rectangular blanks, and particularly square blanks,into hollowballs I have found that it is impossible to get satisfactory re sults when the edges of the points or apices of the cup are straight, as such cups when closed form balls having fiat portions on their surfaces. To overcome this difliculty, animportant step of my present invention consists in drawing the blanks into cups, the points or apices of which have convexlycurved edges, which when brought together in closing the cup insure a substantially accurate spherical surface. Care must of course be exercised in determining the proper sizes of punch and die relatively to the thickness of the metal of the blanks to be formed If the fit is too tight, the metal will be drawn too much, excessively elongating the points or apices, which when their convexly-curved edges are brought together in closing the cup would not form a true sphere. Likewise if the fit is too loose the points or apices would not be sufficiently elqngated, and an untrue sphere would resu t.

The invention will be more readily understood by reference to the accompanying drawings, wherein Figure 1 represents a square blank from which the blank is formed. Fig. 2is an elevation showing the blank struck up into cup form. Fig. 3 is a plan of Fi 2. Fig. 4 is a vertical section of Fig. 2, and Fig. 5 is a plan of a completed ball.

In the production of the ball 31 (shown in Fig. 5) I take a square blank 31, preferably of thin elastic sheet metal, and by stamping the same in dies I depress the center and raise the margins and corners thereof, producing a cylinder or cup 31 (Shown in Fig. 2.) This cylinder or cup has a rounded closed lower end and a serrated upper edge, the points or apices of the serrations being formed by the corners of the blank 31, as will be understood from an examination of Figs. 3 and 1. These points or apices have convexly-curved edges, as clearly shown in Figs. 2 and 4. The diameter of the cup 31 is slightly less than the desired diameter of the finished ball 31 Such ball or spherical structure is produced by again stamping the cylinder or cup 31 between suitably-formed dies and approximating or drawing together the points or apices of said cup, bringing the points and convexlycurved edges thereof together,so as to close the ball on the side opposite the previously-closed rounded part forming the bottom of cup 31*. In the second stamping of the device and the depression and approximation of the apices or points thereof the central portion'zl. e., that part between the rounded bottom and the serrations or apicesis slightly expanded or swelled outwardly, with the advantages above explained, so as to cause the finished ball to have a diameter slightly greater than that of the cup 31*. It will be seen that a ball is made by this process entirely without waste of material and that there is no scrap to clog or otherwise interfere with the workin of automatic machinery. Moreover, the baIl is spherical, resilient, and hollow and exhibits material and considerable resistance to crushing force.

The process of this invention is not limited to the formation of balls, being also applicable to hollow metallic articles departing more or less from a spherical shape.

What I claim is 1. The process of making hollow metallic balls from sheet-metal blanks by stamping said blank into the shape of a cup having a rounded bottom and a serrated rim, and then closing the cup and swellin or expanding the same to form a ball of Iarger diameter than the cup.

2. The process of making hollow metallic balls from a strip of metal by first severing a iece to form a rectangular blank, stamping it into the shape of a cup having a rounded bottom and a serrated rim, and then closing the cup and simultaneously swelling or expanding the same to form a ball of larger diameter than the cup.

3. The process of making hollow metallic balls from a strip of metal by first severing a piece to form a rectangular blank, stamping. it into the shape of a cup having a rounded bottom and a serrated rim, and then closing... the cup and swelling or expanding the same to form a ball of larger diameter than the cup.

4. The process of making hollow metallic balls from sheet metal by first formin a rectangular blank, stamping it into the s ape of a cup having a rounded bottom and a serrated rim, and then closing the cup and swelling or expanding the same to form a ball of larger diameter than the cup.

5. The process of making hollow metallic articles from sheet-metal blanks by stamping said blank into the shape of a cup, and then closing the cup and swelling or expanding the same to form an article of larger diameter articles from sheet-metal blanks by stamping said blank into the shape of a cup, having a serrated rim, and then closing the cup and swelling or expanding the same to form an article of larger diameter thanthe cup.

8. The process of making a hollow metallic article from a rectangular sheet-metal blank by stamping or drawing said blank into the shape of a cup having a closed bottom and a serrated rim, the edges of the points or apices of said rim being convexly curved, and then closing the open end of the cup.

9. The process of making a hollow metallic ball from a rectangular sheet-metal blank by stamping or drawing said blank into the shape of a cup having a rounded bottom and a serrated rim, the edges of the points -or apices of said rim being convexly curved, and then closing the open end of the cup to form a sphere.

10. The process of making a hollow metallie ball from a square sheet-metal blank by 0 stamping or drawing said blank into the shape of a cup having a rounded bottom and a serrated rim, the edges of the points or apices of said rim being convexly curved, and then closing the open end of the cup to form a sphere.

11. The process of making a hollow metallic ball from a square sheet-metal blank by stamping or drawing said blank into the shape of a cup having a rounded bottom and a serrated rim, the edges of the points or apices of said rim being convexly curved, and t en closing the cup and swelling or expanding the same to form a ball of larger diame- -ter than the cup.

In testimony whereof I have signed this specification in thepresence of two subscrib- GEO. T; HALL, R. W. JoHNsroN. 

